Field of the Invention
Various embodiments of the present invention relate to an exhaust gas recirculation system, and more particularly, to a method and a controller for an exhaust gas recirculation system for preventing a valve from sticking which solves the operation condition of an EGR cooler by-pass valve of which the operation is limited under low temperature (cold)/low load of an engine.
Description of Related Art
In general, when an exhaust gas recirculation system (hereafter, referred to as an EGR system) is used, forced intake air can be supplied to an engine by operating a turbocharger with an exhaust gas from the engine and some of the exhaust gas is returned to the engine, thereby further improving the performance of the engine.
Further, the EGR system can considerably contribute to reducing noxious components such as CO, HC, and NOx (nitrogen compound) in an exhaust gas. Accordingly, a diesel engine necessarily requires such an EGR system for reducing NOx. To this end, the EGR system includes an EGR line extending from the front end of the turbine in a turbocharger to an intake manifold, an EGR cooler, an EGR valve, and an EGR cooler by-pass valve (hereafter, referred to as an ECB V/V).
In those parts, the ECB V/V prevents fouling (deterioration of efficiency due to collection of carbon) of the EGR cooler and operates in accordance with engine accumulation for preventing overcooling of an EGR gas. For example, when a vacuum type ECB V/V starts operating in a normal state, a solenoid valve operates against the spring force of a governor keeping the ECB V/V closed, so the ECB V/V is turned on/off by a negative pressure of a vacuum pump.
As repetition of turning-on/off prevents the ECB V/V from sticking due to condensed water or carbon, so it is possible to prevent fouling (deterioration of efficiency due to accumulation of carbon) of the EGR cooler and the EGR gas from being overcooled.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.